It's just seized on the hub from heat and exposure to the elements. You can either kick the snot out of the tire itself (kick it at 3, 6, 9, and 12 o'clock positions), repeatedly until it comes off, or hold a piece of a 2x4 against the tire and hit it with a mallet - hard. Don't hit the wheel, just the tire. Hitting the wheel may dent it, but hitting the tire (or kicking it) won't hurt it. Beat it like that and it'll come off.

Spray around lugs /center hub/and try to where backing of rim comes into contact with hub -rust and road grime have rim semi fused to hub than use a mallet on rim tap areas that were sprayed and smack on tire from front than behind

If say those tires. omg 18 years old
the factory puts on , Tinnerman clips. they aid fast assembly at the plant.
they are flat rectangle clips. if see just force them off and trash them.
or you have a rust issue.
no clips, it's rust. if rust ,one kick of foot and bam its off, if foot weak, a short 4x4 works too.
with a force of say chopping wood to tire side.

Actually there is another lug in the middle under a flat disc holding the tire on